Jim, I just wanted to add that all Royer ribbons are not the same, My favorite Royer is actually the re-issue of the Speiden Ribbon that David Royer licensed from Speiden. Royer calls this the SF1 and the stereo version The SF12. It is really a very nice Ribbon although extremely delicate and easy to damage. It has a very very thin ribbon and therefore has a very nice freq response and color. It sounds great on many things.. I was not so impressed with the Royer 121s and the active ribbons as much.. The 121 has an obvious rise in the low mids and darker mid tone overall a bit like the Beyer 160. It is a more robust ribbon and holds up a bit better if abused. I agree with you that the Coles or RCAs are very nice and will often win out in many situations.
About That question about FM amplifiers... They are very expensive, Have very high Damping Factor and work great as a Large Main Soffit Mounted Speaker amp.. I heard some on The older Hidley Sierra Eastlake TM2 monitors in LA. I thought that amp sounded great on the Low Freq drivers.. Great Damping Factor that resulted in a very detailed and Tight, Punchy Lows. They are extremely expensive though..All those precision matched MosFets.
Thanks for all your time and input on this Forum,
Glenn Brown
engineer/producer
GBP Studios
(home of the Muscle Shoals Neve 8068)